This invention relates to video signals and, more particularly, to apparatus and method for encoding and decoding video signals for use in a compatible high definition television system as well as in other applications.
It is well recognized that it would be desirable to have television exhibit higher definition for the viewer. The Society of Motion Picture and Television Engineers ("SMPTE") convened a study group to study various aspects of high definition television systems, including such systems for use in the home. The SMPTE study group concluded, among other things, that any new service which provides higher definition television than is conventionally broadcast (i.e., more elements per line and lines per frame, and thus a wider bandwidth necessary for transmission) should serve existing home television receivers with essentially all the picture attributes and quality of which the receivers are capable (see SMPTE Journal, Volume 89, No. 3, pp. 153-161, March, 1980). As an example, the study group cited the instance when the NTSC compatible color service was first introduced. Monochrome receivers then in the hands of the public reproduced from the color broadcasts a monochrome version of the broadcast, essentially without compromise either in electronic performance of the receivers or in the quality of the reproduction. The SMPTE study group also noted that receivers designed for new (high definition) service, should be capable of operating using the pre-existing transmissions and derive from them a result not inferior to that provided by pre-existing receivers.
The reports of the SMPTE study group indicated the difficulty of identifying the means by which an acceptable compatible system can be achieved. To applicant's knowledge, no such system has been developed. It is an object of the present invention to set forth a high definition television system which is believed to meet practical requirements of performance and compatibility and have operating parameters sufficiently flexible to fit within standards that are ultimately adopted by television industry.
It is another object of the present invention to provide an encoding and decoding technique that is useful for transmitting or storing video information in a form that requires reduced bandwidth channels or reduced storage size, as the case may be.
It is a further object of the present invention to provide a technique, which takes advantage of characteristics of human vision, for encoding in a new way, transmitted color television signals, such that receivers having a decoder with a frame store (but not necessarily a full high resolution capability) can recover fully separated color and luminance detail.